This invention is directed to an improved mechanism for controlling the lead angle between eccentric weights in a vibratory mechanism. More specifically, this invention is directed to a mechanism allowing controlled privotal movement of one eccentric weight of a dual eccentric weight vibratory system.
A number of lead angle changing mechanisms have been devised for vibratory mills and the like. One such earlier mechanism is disclosed in U.S. patent application Ser. No. 540,507, filed Jan. 13, 1975, for MOTION REVERSING SYSTEM FOR A VIBRATORY MILL, now abandoned. This earlier mechanism incorporated a reversible motor having a fixedly mounted eccentric weight on one end of the motor shaft. At the other end of the motor shaft, a rotatably mounted eccentric weight is constrained to pivot relative to the shaft only through a predetermined angle. The direction of rotation of the motor determines the position of the rotatably mounted eccentric weight within that predetermined angle.
This passive weight mounting system has worked advantageously with vibratory mills and the like to control the characteristics of the induced vibratory motion of such devices. However, in some instances, when a high torque motor has been employed with such a lead angle controlling mechanism, it has been found that over a period of time the impacting of the rotatably mounted eccentric weight on the mechanism limiting rotation has resulted in damage to the system. In this context, a means for reducing the impact loads occurring in the operation of such mechanisms was felt to be advantageous. Other, active systems have been employed to change lead angles of vibratory devices during operation. Such devices have used pneumatic systems and the like to accomplish the required lead angle change. The increased complexity of such systems is believed to be disadvantageous because of the increased possibility of system failure in such a dynamic environment and because of the increased costs.